With technological advances of recent years, television viewing is becoming more of an interactive experience. For example, rather than just broadcasting a television signal to be received by an antenna, cable television systems have been developed to broadcast television signals as well as other information, such as an up to date electronic program guide (EPG), to television set-top boxes that receive and process the data. High-end set-top boxes may be configured to support other applications as well, such as an Internet browser application. Other interactive applications may also be enabled over a cable television network, such as a user viewing log collection application, an instant messaging application, an email application, and so on.
Cable television systems (herein referred to as a headend) typically broadcast television programs over what is referred to as an in-band network, and broadcast EPG data and other such data over what is referred to as an out-of-band network. An in-band network may typically include hundreds of channels, each having a large bandwidth (e.g., capable of carrying 38 Mbps). The in-band network is used for one-way communication of data from the headend to the set-top boxes.
On the other hand, the out-of-band network typically consists of only one channel, and supports two-way communication, but with very limited bandwidth that must be shared by multiple set-top boxes on a particular network. Furthermore, the bandwidth available for transmitting data to the set-top boxes may be greater than the bandwidth available for receiving data from the set-top boxes. For example, a typical out-of-band channel may support the transfer of 2 Mbps of data from the headend to the set-top boxes (i.e., downstream) and 256 Kbps of data from the set-top boxes to the headend (i.e., upstream).
Furthermore, most cable television systems are configured to use a data transfer protocol in which it is common for data packets to collide and be lost, with no notification to the sender that the data was lost.
With an increased desire for interactive data applications to be available to cable television viewers over the cable television broadcast system, a need exists for reliable two-way data communication between a headend and multiple set-top boxes over the out-of-band network.